1. Field of the Invention
The present invention relates to a motor drive controller and a control method of the motor drive controller, and more particularly, to a motor drive controller that controls a rotation speed of a motor based on an external input signal and a control method of the motor drive controller.
2. Description of the Related Art
A method of controlling a rotation speed of a motor (for example, a brushless DC motor which is used as a fan motor or a motor of an electric fan) using a motor drive controller is known in which an external command signal is input and the rotation speed of the motor is controlled based on the command signal. An example of the command signal is a pulse-width modulation (PWM) signal and a rotation speed of a motor is controlled based on a duty ratio of the PWM signal.
An example of such configuration is disclosed in JP-A-2014-036571. The publication JP-A-2014-036571 discloses a configuration of a motor speed controller that controls a motor by setting an actual rotation speed based on a target speed that is externally input.
The controller described in JP-A-2014-036571 may have the following problems. That is, a target rotation speed is designated by inputting a command signal such as a clock signal or a PWM signal that is externally input to the motor speed controller. An equipment manufacturer who mounts the motor speed controller on equipment may need to input a command signal to the motor speed controller such that the motor operates at a target rotation speed depending on specifications or settings of the equipment. When the target rotation speed of the motor is changed, the equipment manufacturer may need to change the command signal. However, the configuration for inputting the command signal to the motor speed controller may not be easily configured.
As a solution to this problem, for example, use of a command signal (for example, a high/low-combined signal) capable of easily changing the target rotation speed can be considered unlike the configuration described in JP-A-2014-036571. The target rotation speed can be changed in a simple method using such a signal. However, in using such a signal, the number of signal patterns which can be used to set the target speed, and the like, is relatively small. Accordingly, there may be a problem in that a range in which the target rotation speed can be changed is narrow (the degree of freedom is low).